Method for controlling an automatic transmission

ABSTRACT

A method for controlling an automatic transmission driven by an internal combustion engine is proposed in which a shift from a first to a second transmission ratio occurs as a pull upshift by a first clutch opening and a second clutch closing and electronic transmission control unit controls via electromagnetic valves the pressure curve of the first and of the second clutch during the shifting operation. The shifting operation is divided into different shifting phases, an engine intervention taking place within the gradient-adjustment (GE), the sliding (GL), the gradient-reduction (GA) and the closing (S) phases, an engine torque being reduced by an engine intervention factor (mdzegs) being transferred from the transmission control device to an engine control device of the internal combustion engine.

The invention relates to a method for controlling an automatictransmission driven by an internal combustion engine in which a shiftfrom a first to a second transmission ratio occurs in the form of a pullupshift. Here a first clutch opens and a second one closes and anelectronic transmission control device controls, via electromagneticvalves, the pressure curve of the first and of the second clutch duringthe shifting operation. The latter consists of a rapid-filling, afilling-equalization, a load transfer, a gradient-setting, a sliding, agradient-reduction and a closing phase.

Such a method is known already from the Applicant's laid openapplication DE 44 24 456 A1 which is included by explicit reference inthe contents of the preamble of the instant patent application. In thispublication is particularly proposed to use this method in a grouptransmission.

From the prior art (“The Engine Intervention”—a new element of theelectronic transmission control by Manfred Schwab and Alfred Müller,Bosch, Technical Reports 7, 1983, pp. 166 to 174) is known, in general,to effect an engine intervention during a shifting operation, it beingpossible by an exactly time controlled curve of the engine torque duringshifting operation of an automatic transmission to optimize the controlof the transmission with regard to shifting comfort, service life of thefriction elements and to the transmissible power of the transmission. Byengine intervention is to be understood all steps which, during ashifting operation in the transmission, allow purposefully to modulate,especially to reduce, the engine torque generated by the combustionprocess. Due to the legislator's strict requirement on the reaction timeand the time cycle of the control during a total duration of theintervention of only about 500 ms, a precisely timed coordination of theshifting operation is required. An engine intervention can be used bothin upshifts and downshifts. The primary object of the engineintervention in upshifts is to reduce the energy loss produced in thefriction elements during the shifting operation by reducing the enginetorque during the synchronization process without interrupting thetraction. The tolerance obtained thereby can be used to increase theservice life of the friction partners by abbreviating the grinding time.

From DE 42 09 091 A1 is further known already a method for reducing theengine torque during a gear shift in a motor vehicle. The energy torquewhich results from rotating masses to be retarded or accelerated duringa change of speed of the rotation angle of the engine determined by agear change is calculated and the engine torque is reduced duringcoupling of the new transmission gear by the amount of the energytorque.

Methods of the above mentioned kind are subject to constant furtherdevelopments with regard to an optimal use of the engine interventionwith the smallest possible load of the shifting elements, the same as anoptimal torque curve that takes into account the directives of theengine manufacturer, especially in relation to the limits of the maximumpossible engine intervention with regard to mixture and exhaustconditions.

The problem to be solved by this invention is to indicate an optimizeduse of the engine intervention especially requiring a minimal adaptationexpense, that is, in an analytic calculation process, for ex., thefewest possible parameters are needed.

According to the invention, this problem is solved in a method of thekind above indicated with an engine intervention by a reduction of theengine torque occurring within the gradient-setting, sliding,gradient-reduction and closing phases, an engine intervention factorbeing transmitted from the transmission control device to an enginecontrol device of the internal combustion engine. Thereby isadvantageously obtained that the pressure curve set of the second,closing clutch and the friction torque resulting therefrom, the same asthe torque generated by the intervention factor and emitted by theengine, is optimally matched in time without need of expensiveadaptation parameters and expense.

In one development of the invention, it is proposed that a maximumengine intervention factor mdzegsomax be calculated from a maximumdynamic torque M_DYN, a static torque without engine intervention M_STATand a maximum adjustable engine characteristic factor KF_MDZ MAX.

The maximum engine intervention factor mdzegsomax is calculated as theratio of the dynamic engine torque M_DYN to the static engine torqueM_STAT.

This applies to the case that the value thus calculated be smaller thanthe maximum adjustable engine characteristic factor KF_MDZ MAX. But incase the value, thus calculated, is greater than the maximum adjustableengine characteristic factor KF_MDZ MAX, then the maximum engineintervention factor mdzegsomax corresponds to the maximum adjustableengine characteristic factor KF_MDZ MAX.

In a special development of the invention is proposed that the engineintervention factor mdzegs in the gradient-setting phase GE be linearlyincreased all along beginning from a value zero to the value of themaximum engine intervention factor mdzegsomax. In the sliding phase GLthat follows, the engine intervention factor mdzegs is maintainedessentially constant at the value mdzegsomax and in thegradient-reduction phase GA and closing phase S that follow the engineintervention factor mdzegs is reduced from the maximum engineintervention factor mdzegsomax to the value zero.

The pressure on the second clutch P_K to close is advantageouslycalculated from the static engine torque with engine intervention M_STATME, the dynamic engine torque M_DYN, a factor F1 and a converterreinforcement WV, the same as the absolute pressure P_ABS.

The static engine torque with engine intervention M_STAT ME iscalculated as the product from the static engine torque M_STAT by thesum of one minus the engine intervention factor mdzegs.

The clutch pressure P_K at the start of the engine intervention, namely,at the start of the GE phase, is calculated as the sum of the absolutepressure P_ABS and the static engine pressure P_M STAT which iscalculated as product from the factor F1 by the static engine pressureM_STAT by the converter reinforcement WV, the absolute pressure P_ABSbeing the pressure required to overcome the recoil spring tensions andthe friction on the actuating piston.

The clutch pressure P_K during the sliding phase GL is calculated as thesum of the absolute pressure P_ABS and the pressure P_M STAT ME of thestatic engine torque with engine intervention and the pressure P_M DYNof the dynamic engine torque, the pressure P_M DYN being calculated asthe product from the factor F1 by the converter reinforcement WV by thedynamic engine torque M_DYN.

According to the invention the pressure of the second closing clutchduring the pull upshift takes the following course: In the rapid-fillingphase SF, the clutch is loaded with high pressure, in thefilling-equalization phase FA; it is filled to a lower pressure levelP_ABS and, in the load-transfer phase LÜ, the pressure is increased toan end value P_ABS+P_M STAT. In the gradient-setting phase GE, thepressure is increased from the value P_ABS+P_M STAT to a new end valueP_ABS+P_M STAT ME +P_M DYN and in the sliding phase GL be kept constantuntil reaching a pre-synchronizer point VSYNC. Then follows thegradient-reduction phase GA in which the pressure is reduced to an endvalue P_ABS+P_M STAT and upon reaching the end value the closing phasesS1 and S2 begin.

It is proposed in a development of the invention that the beginning ofthe engine intervention for synchronization with the shifting pressurebuild-up in the phases GE and GL be delayed, via a time step, when thereaction for the engine intervention is quicker than the reaction to thepressure directives. Thereby is advantageously obtained that the outputtorque be not unnecessarily reduced.

In reversal of the above mentioned features, it is proposed that thebeginning of the shifting pressure build-up for synchronization with theengine intervention in the phases GE and GL be delayed, via a time step,when the reaction of the engine intervention is slower than the reactionto the pressure directives. Thereby unnecessary friction stresses on theshifting elements can be advantageously prevented.

In a development of the invention, the dynamic engine torque M_DYN isincreased during the gradient-setting phase GE from 0 to 100%, in thesliding phase GL it remains at 100% and, in the gradient-reduction phaseGA that follows, the dynamic engine torque M_DYN is again reduced from100% to 0.

The engine intervention for the rest is activated only when the enginerotational speed exceeds a preset value whereby a stalling of the engineis advantageously prevented.

The maximum possible engine intervention factor mdzegsomax isadvantageously stored in a characteristic field according to operatingparameters such as of the engine rotational speed, of the load position,or of the injection amount, or of the engine torque, or of the air mass.

The maximum adjustable engine characteristic factor KF_MDZ MAX isreported back from the engine control device to the transmission controldevice whereby a quick regulation of the engine intervention factor ismade possible.

Other objects, features, advantages and possible utilizations of theinvention result from the description that follows of the embodimentshown in the figures. All the features described and/or graphicallyshown constitute the object of the invention by themselves or in anylogical combination independently of their compilation in the claims andtheir references to other claims. In the drawing:

FIG. 1 is the curve of the engine intervention factor mdzegs in thecourse of time; and

FIG. 2 is the curve of the pressure P_K of the second closing clutch inthe course of time.

The engine intervention factor mdzegs (FIG. 1) starts at the beginningof the gradient-setting phase GE from a value zero along the linemdzegso linearly to the maximum engine intervention factor mdzegsomax.The latter is reached with the end of the gradient-setting phase GE. Thevalue then remains constant during the sliding phase GL and at the startof the gradient-reduction phase GA until the end of the closing phase S1is linearly reduced down to the zero value.

The curve of the engine intervention factor mdzegs is delayed in timeand occurs with an increase changed in relation to the unfiltered curvemdzegso along the line mdzegs when the reaction of the engineintervention is quicker than the reaction to the pressure directives.

The curve of the pressure P_K for the second clutch to close (FIG. 2)begins at the pressure value zero for the time interval in which the oldgear AG still is coupled. This is followed by a rapid-filling phase SFin which the clutch to close is loaded with high pressure. In thefilling-equalization phase FA that follows occurs a filling of theclutch with a pressure of lower level P_ABS, which corresponds to thepressure required to overcome recoil spring tensions and the friction onthe actuating piston. Thereafter the pressure P_K is linearly increasedto a value P_ABS+P_M STAT.

In the gradient-setting phase GE that follows, the curve of the pressurerises to a pressure level corresponding to a value P_ABS+P_M STAT ME+P_M DYN. The value is maintained constant until the end of the slidingphase GL, the moment corresponding to the pre-synchronizer point VSYNC,and then, in the gradient-reduction phase GA, it is reduced almost tothe pressure P_ABS+P_M STAT already existing at the beginning of thegradient-setting phase GE. In reality the synchronizer point SYNCappears before the ideal synchronizer point after the time T_RASYN. Inthe closing phase S1 then occurs one other linear increase of thepressure P_K and simultaneously the termination of the ignitionintervention. Until adhering of the friction linings of the secondclutch to close, at the end of the closing phase S2 there follows oneother pressure increase of the second clutch. Starting from this moment,the maximum clutch pressure P_MAX is reached and a new gear NG isswitched in.

The two phases load transfer LÜ and gradient setting GE are also jointlydesignated as the phase of the ramp of the load-transfer T_RALUE. Duringthe gradient-reduction phase GA, the curve of the pressure P_Kcorresponds to the ramp from the change of the dynamic torque. Theclosing phase S1 corresponds to a closing ramp plus a ramp from thechange of the engine torque while the pressure curve in the subsequentphase S2 follows the closing ramp exclusively.

What is claimed is:
 1. A method for controlling an automatictransmission driven by an internal combustion engine in which a shiftfrom a first to a second transmission ratio occurs in the form of a pullupshift by a first clutch opening and a second clutch closing wherein anelectronic transmission control device controls, via electromagneticvalves, the pressure curve of the first and of the second clutch duringthe shifting operation and the shift consists of a rapid-filling (SF), afilling-equalization (FA), a load-transfer (LÜ), a gradient setting(GE), a sliding (SL), a gradient-reduction (GA) and a closing (S) phase,wherein the gradient-setting (GE), the sliding (GL), thegradient-reduction (GA) and the closing (S) phases the engineintervention is effected by a reduction of the engine torque (M_MOT), anthe engine intervention factor (mdzegs) being transmitted from atransmission control device to an engine control device of the internalcombustion engine, and wherein a clutch pressure (P_K) on the closingclutch is calculated from a static engine torque with engineintervention (M_STAT ME), a dynamic engine torque (M_DYN), a factor(F1), a converter reinforcement (WV) and an absolute pressure (P_ABS),the static engine torque with engine intervention (M_STAT ME) beingcalculated as the product from the static engine torque (M_STAT) by thesum of one minus the engine intervention factor (mdzegs).
 2. The methodaccording to claim 1, wherein the engine intervention factor (mdzegs) inthe phase (GE) is linearly increased in the course of time from zero tothe value of the maximum engine intervention factor (mdzegsomax), in thephase (GL) it is maintained substantially constant and in the phase(GA)+(S) it is reduced from the maximum engine intervention factor(mdzegsomax) to zero.
 3. The method according to claim 2, wherein amaximum engine intervention factor (mdzegsomax) is calculated from amaximum dynamic torque (M_DYN), a static engine torque without engineintervention (M_STAT) and a maximum adjustable engine characteristicfactor (KF_MDZ MAX).
 4. The method according to claim 2, wherein themaximum engine intervention factor (mdzegsomax) is calculated as theratio of the dynamic engine torque (M_DYN) to the static engine torque(M_STAT) in the case that said value be smaller than the maximumadjustable engine characteristic factor (KF_MDZ MAX), and in case saidcalculated value be greater than the maximum adjustable enginecharacteristic factor (KF_MDZ MAX), the maximum engine interventionfactor (mdzegsomax) corresponds to the maximum adjustable enginecharacteristic factor (KF_MDZ MAX).
 5. The method according to claim 1,wherein the clutch pressure (P_K) at the beginning of the engineintervention, namely, at the beginning of the phase (GE), is calculatedas the sum of the absolute pressure (P_ABS) and the static enginepressure (P_M STAT), the latter being calculated as product of thefactor (F1) by the static engine torque (M_STAT) by the converterreinforcement (WV).
 6. The method according to claim 1, wherein theclutch pressure (P_K) during the sliding phase (GL) is calculated as thesum of the absolute pressure (P_ABS) and the pressure (P_M STAT ME) ofthe static engine torque with engine intervention and the pressure (P_MDYN) of the dynamic engine torque, (P_M DYN) is calculated as theproduct of the factor (F1) by the converter reinforcement (WV) and thedynamic engine torque (M_DYN).
 7. The method according to claim 1,wherein the second clutch in the pull upshift during the rapid-fillingphase (SF) is loaded with high pressure, in the filling-equalizationphase (FA) it is filled to a lower pressure level (P_ABS) and in theload-transfer phase (LÜ) the pressure of the second clutch is increasedto an end value (P_ABS+P_M STAT) and in the gradient-setting phase (GE)the pressure is increased from the end value (P_ABS+P_M STAT) to an endvalue (P_ABS+P_M STAT ME+P_M DYN), in the sliding phase (GL) thepressure remains constant until a pre-synchronous point (VSYNC) isdetected, in the gradient-reduction phase (GA) the pressure of thesecond clutch is reduced to an end value (P_ABS+P_M STAT) and uponreaching the end value the closing phase (S1, S2) begins.
 8. The methodaccording to claim 1, wherein the start of the engine intervention forsynchronization with the shifting pressure build-up in the phases (GE)and (GL) is delayed during a period when the reaction of the engineintervention is quicker than the reaction to the pressure directives. 9.The method according to claim, 1, wherein the beginning of the shiftingpressure build-up for synchronization with the engine intervention inthe phases (GE) and (GL) is delayed during a period when the reaction ofthe engine intervention is slower than the reaction to the pressuredirectives.
 10. The method according to claim 1, wherein the dynamicengine torque (M_DYN) during the gradient-setting phase (GE) isincreased from zero to 100%, in the sliding phase (GL) it remains at100% and in the gradient-reduction phase (GA) it is reduced from 100% tozero.
 11. The method according to claim 1, wherein the engineintervention is activated when the engine rotational speed exceeds apreset value.
 12. The method according to claim 1, wherein the maximumpossible engine intervention factor (mdzegsomax) is stored in acharacteristic field according to operating parameters such as enginerotational speed, load position, or injection amount, or engine torque,or air mass.
 13. The method according to claim 1, wherein the maximumadjustable engine characteristic factor (KF_MDZ MAX) is actuallyreported back from the engine control device to the transmission controldevice.